Thermoplastic starch composition derivatives from agricultural byproducts

ABSTRACT

A thermoplastic starch composition acquired from compounding a mixture comprising starch-containing agricultural byproducts in 45 to 70% by weight of total composition, the agricultural byproducts having a starch content less than 50% dry weight; thermoplastic synthetic polymer in 25 to 50% by weight of total composition; plasticizer in 1 to 10% by weight of total composition; and coupling agent in 1 to 5% by weight of total composition; the compounding performed at a first temperature which is higher than room temperature.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/371,982, filed Jul. 11, 2014, which is a national stage ofInternational Application No. PCT/MY2012/000278, filed Nov. 21, 2012,and which claims priority to and benefit of Malaysian Patent ApplicationNo. PI 2012700072, filed Mar. 13, 2012; the entirety of each of theaforementioned applications is hereby incorporated by reference.

FIELD OF INVENTION

The present invention relates to a thermoplastic starch composition.More specifically, the disclosed thermoplastic starch composition isproduced utilizing agricultural waste containing relatively low starchcontent under an optimized process.

BACKGROUND OF THE INVENTION

Starch is a natural polymer composed mainly of two majorpolysaccharides, namely the linearly linked amylose and the branchedamylopectin. Starch possesses thermoplastic behavior though it exits ingranular form in its natural state. Starch can be transformed into atmolten plastic state, known as thermoplastic starch (TPS), whensubjected to shearing force at a temperature of 90 to 180° C. in thepresence of suitable plasticizer. In the thermoplastic starch, theweaker hydrogen bond between the polysaccharides and the plasticizerreplaces the original inter-polysaccharides hydrogen bond rendering thethermoplastic starch soft and ductile. Specifically, the new bondingbetween the plasticizer and the polysaccharides greatly reduces thesecondary bonds holding the long chain polysaccharides. In view of thatstarch is a renewable resource, thermoplastic starch is a sustainableproduct. Yet, it suffers from two major shortcomings, high watersolubility and poor mechanical strength, compared to conventionalsynthetic plastic. In order to improve TPS mechanical property andreduce its water absorbing properties, modification have been made tothe TPS. For example, European patent application no. 0327505 describesa polymeric blend of TPS and water insoluble synthetic thermoplasticpolymer claiming a derived polymeric composition with better mechanicalproperty and reduced water solubility. Guy et. al. claims another TPSderived thermoforming compound containing at least one hydroxycarboxylicacid salt that the compound acquired is claimed to have maximum losstangent in wide range of temperature in Canadian patent application no.2060409. Further TPS modification can be found in International patentpublication no. 03074604 which provides TPS-grafted polymers formedusing compatibilizer instead of plasticizer to reduce water absorptioninto the formed polymer. Co-continuous TPS substantially free of wateris described in U.S. Pat. No. 6,605,657 and TPS reinforced byparticulate filler is disclosed in another U.S. Pat. No. 6,231,970.

In recent years, a lot of effort has been put into utilizingagro-industrial wastes for the manufacturing of value-added productssuch as biofuels, biomaterials and the like. Recycling theseagro-industrial waste can alleviate environmental problems associatedwith the waste disposal and reduce dependence on petroleum resources.Considering that TPS is a product necessary using starch as the majorforming constituent, it is practical to employ such waste ofagro-industrial in its production as long as some technical problemsinherited from such use are solved. For instance, agro-industrial wastecontains much lower starch content compared to normal starch granulethat TPS derived thereof may fail to attain the desired plasticity anddegradability. Yet, the present invention provides an agriculturalwaste-derived TPS composition possessing physiochemical properties whichmeets the industrial acceptable standard in terms of mechanicalproperties as well International definition for a bio-based material.

SUMMARY OF THE INVENTION

The present invention aims to provide a thermoplastic starch (TPS)composition derived from agro-industrial waste. More precisely, theagro-industrial waste used in the present invention is relatively lowerin starch content and have subjected to special processing stage inorder to achieve the desired property.

Another object of the disclosed invention is to disclose a polymercomposition containing at least 25% by weight of renewable carbon basedon test method in The American Society For Testing and Material (ASTM)D6866 meeting the bio-based standard as setting forth by the JapanBioPlastic Association (JBPA), United State Department of Agriculture(USDA) as well as DIN Certco and Vincotte in Europe.

Further object of the disclosed invention is to offer a TPS compositionof agro-industrial waste being acquired through a single compoundingprocess through a unique screw configuration in the extrusion stage.

Still, another object of the disclosed invention is to offer a TPScomposition obtained from pre-treated agro-industrial waste.

At least one of the preceding objects is met, in whole or in part, bythe present invention, in which one of the embodiments of the presentinvention includes a thermoplastic starch composition acquired fromcompounding a mixture comprising starch-containing agricultural waste in45 to 70% by weight of total composition that the agricultural wastecontains starch content less than 50% in dry weight; thermoplasticsynthetic polymer in 25 to 50% by weight of total composition;plasticizer in 1 to 10% by weight of total composition; and couplingagent in 1 to 5% by weight of total composition; wherein the compoundingis performed at a first temperature which is higher than roomtemperature. Preferably, the agricultural waste is pre-treated orfunctionalized with a reactant having functional group selected from thegroup consisting of primary alkylamine, secondary alkylamine, tertiaryalkylamine, stearate ester, oleate ester, ecucate ester, ethoxy,methoxy, silane, vinyl, hydroxyl or any combination thereof at a secondtemperature, which is higher than room temperature but lower than thefirst temperature, prior to compounding the mixture. More preferably,the agricultural waste is pulverized powder of tamarind kernel,ratanjot, castor seed, Jatropha seeds, moringa seed, neem seed, cocoabean skin, coffee bean skin, rice husk, sugar cane bagasse, coconutfiber, palm oil fruit bunch, wood chips, and saw dust.

In another respect, the thermoplastic synthetic polymer is vinylpolymer,polystyrenes, polylactic acid, polyhydroxyl adipate or polyvinylalcohol, polyacrylonitriles, polyvinylcarbazols, poly(alkylene oxides),poly(hydroxy butyrate), polyimides, polyarylethers, poly(alkyleneterepthalates), polycarbonates, polyester, polypropylene, polyethylene,and polyisobutylenes.

In another aspect, the disclosed TPS composition further comprises aninitiator in 0.01 to 5% by weight of total composition, wherein theinitiator is selected from any one or combination of sodium peroxide,tert-butyl hydroperoxide, di-tert-butyl peroxide, and dicumyl peroxide.

In another aspect, the mixture further comprises filler in 25 to 35% byweight of total composition that the natural filler is pulverized powderof any one or combination of wood, kenaf, coconut husk and rice husk.Preferably, the pulverized powder has a particle size not more than 170micron.

In another aspect, the mixture further comprises a processing aid in 0.2to 2% by weight of total composition selected from any one orcombination of non-metallic stearates, paraffin wax, polyester wax,stearyl stearate, distearyl phthalate, pentaerythritol adipate stearate,ethylene glycol distearate, pentaerythritol tetrastearate, glyceroltristearate, polyethylene glycol monostearate, glycerol monooleate,glycerol distearate, N,N-ethylene bis-stearamide, fatty acidsderivatives and the like.

In another aspect, the mixture further comprises plasticizer in 0.01 to10% by weight of total composition. Preferably, the plasticizer used inpreparing the TPS composition is any one or combination of sugaralcohol, polyols, sorbitl ethoxylate, glycerol ethoxylate,pentaerythritol ethoxylate, sorbitol acetate, pentaerythritol acetate,water, urea or area derivatives, anhydrides of sugar alcohols, phthalateesters, dimethyl and diethylsuccinate and related esters, glycerolmonoacetate, glycerol diacetate, glycerol triacetate, glycerol mono acidesters, citric acid esters, adipic acid esters, stearic acid esters,oleic acid esters, copolymers of ethylene and acrylic acid, polyethylenegrafted maleic acid, polybutadiene-co-acrylic acid,polybutadiene-co-maleic acid, propylene-co-acrylic acid,polypropylene-co-maleic acid and other hydrocarbon based acid, adipicacid derivatives, benzoic acid derivatives citric acid derivatives,phosphoric acid derivatives, sebacic acid derivatives, monoglyceride,diglycerides, acetylated monoglyceride, acetylated glycerolmonostearate, acetylated glycerol monoester-12-hydroxystearic acid,esters of glycerin, glycerol monopropionate, glycerol dipropionates andtripropionates, butanoates, stearates, alkylamides, trimethylolpropane,dimethyl sulfoxide, mannitol monoacetate, and mannitol monoethyoxylate.

In another aspect, the first blend further comprises coupling agent in0.01 to 5% by weight of total composition. Preferably, the couplingagent is any one or combination of ethylene vinyl acetate, ethylenevinyl alcohol, polyethylene-co-acrylic acid, polyethylene grafted maleicanhydride, maleic anhydride modified polyolefin, maleic anhydride,acrylic acid, vinyl acetate, vinyl alcohol, amino, amide or acrylate,polyvinyl-alcohol-co-vinyl acetate copolymer, ethylene/vinylalcohol/vinyl acetate copolymers, ethylene/vinyl chloride/vinylalcohol/vinyl acetate graft copolymers, vinyl alcohol/vinylacetate/vinyl chloride/diacryl amide copolymers, vinyl alcohol/vinylbutyral copolymers, vinyl alcohol/styrene copolymers, poly acrylicacid-co-vinyl acetate copolymer, ethylene/acrylic acid/vinyl acetatecopolymers, ethylene/vinyl chloride/acrylic acid/vinyl acetate graftcopolymers, acrylic acid/acrylonitrile copolymer,ethylene/propylene/acrylic acid copolymer, styrene/acrylic acidcopolymers, vinyl benzyl amino ethyl amino propyl trimethoxy silane,glycidyl methacrylate modified polymers, graft copolymers of methylmethacrylate

According to another preferred embodiment, the disclosed invention is anextruded thermoplastic starch composition comprising starch-containingagricultural waste in 45 to 70% by weight of total composition that theagricultural waste contains starch content less than 50% in dry weight;thermoplastic synthetic polymer in 25 to 50% by weight of totalcomposition; plasticizer in 1 to 10% by weight of total composition; andcoupling agent in 1 to 5% by weight of total composition; wherein theagricultural waste and the plasticizer are premixed to form a firstblend while the thermoplastic synthetic polymer and the coupling agentare premixed to form a second blend prior to extruding the first andsecond blends together at a screw extruder having a length/diameterratio of 30 to 40 by a speed of 200 to 300 rpm under 140° C. to 170° C.to produce the thermoplastic starch composition. Likewise, thispreferred embodiment may further include an initiator in 0.01 to 5% byweight of total composition, wherein the initiator is selected from anyone or combination of Sodium peroxide, Tert-butyl hydroperoxide,Di-tert-butyl peroxide, and Dicumyl peroxide

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the system boundary for the lifecycle assessment study on the TPS composition in Example 1;

FIG. 2 is a graph showing calculated energy consumption of differentproduced TPS composition compared to the disclosed TPS composition; and

FIG. 3 is a graph showing calculated carbon footprint of the disclosedTPS composition compared to TPS compositions derived from othermaterial.

DETAILED DESCRIPTION OF THE INVENTION

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objects and obtain the endsand advantages mentioned, as well as those inherent therein. Theembodiment describes herein is not intended as limitations on the scopeof the invention.

The “TPS composition” described herein throughout the specification andthe appended claims refer to blended polymeric material havingthermoplastic starch as constituent and containing one or more additivessuch as thermoplastic synthetic polymer, coupling agent, filler,antioxidant, coloring agent, masterbatch and the like in molten or solidstate.

The present invention is a thermoplastic starch composition acquiredfrom compounding a mixture comprising starch-containing agriculturalwaste in 45 to 70% by weight of total composition that the agriculturalwaste contains starch content less than 50% in dry weight; thermoplasticsynthetic polymer to 25 to 50% by weight of total composition;plasticizer in 1 to 10% by weight of total composition; and couplingagent in 1 to 5% by weight of total composition; wherein the compoundingis performed at a first temperature which is higher than roomtemperature. Preferably, the agricultural waste is pre-treated orfunctionalized with a reactant having functional group selected from thegroup consisting of primary alkylamine, secondary alkylamine, tertiaryalkylamine, stearate ester, oleate ester, ecucate ester, ethoxy,methoxy, silane, vinyl, hydroxyl or any combination thereof at a secondtemperature, which is higher than room temperature but lower than thefirst temperature, prior to compounding the mixture. Bringing thesereactants with specified functional groups into contact with theagricultural waste prior to the compounding process at the secondtemperature improves wettability of the agricultural waste renderingbetter production of the compounded thermoplastic starch composition.Preferably, the reactant is 0.5 to 2.0% by weight of total composition.More preferably, the first temperature mentioned herein ranges between140 to 170° C. and the second temperature is about 65 to 105° C.

According to another preferred embodiment, the functionalisedagricultural waste and the plasticizer are premixed to form a firstblend while the thermoplastic synthetic polymer and the coupling agentare premixed to form a second blend prior to compounding the first andsecond blends together to produce the thermoplastic starch composition.Preparing the components into separated blends in the present inventionmay further improve the yielded thermoplastic starch composition.Accordingly, the first blend and second blend are processed in singleextrusion step to form the desired TPS composition.

Still, in another preferred embodiment, TPS composition can be acquiredthrough processing the first and second blends in the optimizedcondition without having the agricultural waste being functionalised bythe reactant. Particularly, it is an extruded or compoundedthermoplastic starch composition comprising starch-containingagricultural waste in 45 to 70% by weight of total composition that theagricultural waste contains starch content less than 50% in dry weight;thermoplastic synthetic polymer in 25 to 50% by weight of totalcomposition; plasticizer in 1 to 10% by weight of total composition; andcoupling agent in 1 to 5% by weight of total composition; wherein theagricultural waste and the plasticizer are premixed to form a firstblend while the thermoplastic synthetic polymer and the coupling agentare premixed to form a second blend prior to extruding the first andsecond blends together at a screw extruder having a length/diameterratio of 30 to 60 by a speed of 200 to 300 rpm under 140° C. to 170° C.to produce the thermoplastic starch composition.

Preferably, the agricultural waste employed in different embodiments ofthe present invention is pulverized powder of, but not limited to,tamarind kernel, ratanjot, castor seed, Jatropha seeds, moringa seed,neem seed, cocoa bean skin, coffee bean skin, rice husk, sugar canebagasse, coconut fiber, palm oil fruit bunch, wood chips, and saw dust.Apart from that, the disclosed TPS composition can utilize as well solidwaste produced in starch processing activities from food crops liketapioca, yam, taro, konjac, potato or burdock. The agricultural wasteused in the present invention is relatively lower in starch contentcompared to commercially available product. Particularly, theagricultural waste of the present invention contains starch content lessthan 50% more preferably 15% to 50%, in dry weight and amylose contentlower than 20%. Food crops used in conventional TPS production containsmore than 70% in dry weight of starch content and amylose content notlower than 25% by weight. Presence of large amount of non-starchmaterial, such as fibre content not lower than 10% by weight, in thesewastes can significantly affect mechanical property and plasticity ofthe formed TPS composition. To produce TPS composition meetingindustrial standard from these wastes, the agricultural waste needs tobe functionalised first in order to react better with the rest of thecomponents in the subsequent compounding process. Or having theagricultural waste and other ingredients for the production of the TPSpreferably prepared into two different blends prior to compounding orextruding the two blends, namely the first blend and the second blend,together to finally acquire the TPS composition without going throughthe functionalising step. Essentially, the first blend in the presentinvention comprises mixture of the starch-containing agricultural wasteand the plasticizer. The starch-containing agricultural waste and theplasticizer are pre-mixed in a mixer at the speed of 50 to 500 rpm for aduration of 5 to 30 minutes. In contrast, the thermoplastic syntheticpolymer and the coupling agent are premixed using a low shear mixer ortumbler mixer for a period of 10 to 30 minutes rather than beingsubjected to high shearing force in the pre-mix of first blend.According to one embodiment, both first blend and second blend are fedand processed in a twin screw extruder with a length to diameter ratioof 30 to 60, more preferably at 50 to 55, in a temperature of 140 to170° C. with screw speed of 200 to 300 rpm. The elevated temperature inthe extruder melts portion of mixed the first and second blends toproduce the TPS composition. Further, the screw is configured to handlehigh vapour volume generated from the starch-containing agriculturalwaste during mixing. Nevertheless, the disclosed TPS composition can beobtained as well through firstly subjecting the agricultural waste tofunctionalising and subsequent blends preparation prior to finalcompounding.

Preferably, the thermoplastic synthetic polymer employed in the presentinvention is water insoluble. The thermoplastic synthetic polymer can bevinylpolymer such as poly(vinyl chloride) and poly(vinyl acetates),polystyrenes, polylactic acid, polyhydroxyl adipate or polyvinylalcohol, polyacrylonitriles, polyvinylcarbazols, poly(alkylene oxides),poly(hydroxy butyrate), polyimides, polyarylethers, poly(alkyleneterephthalates), polycarbonates, polyester, polyolefin likepolypropylene, polyethylene, and polyisobutylenes. It is likely as wellthermoplastic copolymers like ethylene/vinyl acetate copolymer,ethylene/vinyl alcohol copolymer, ethylene/acrylic acid copolymers,ethylene/ethyl acrylate copolymers, ethylene/methyl acrylate copolymers;acrylonitrile/butadiene/styrene copolymer, styrene/acrylonitrilecopolymer or any combination derived thereof to be used for productionof the disclosed TPS composition. The amount of thermoplastic syntheticpolymer used in the present invention preferably ranges from 25 to 50%,more preferably in between 25 to 40% by weight of total composition.

In order to produce the disclosed TPS composition through a singleextrusion process, an initiator in an amount of 0.01 to 5% by weight oftotal composition is added to initiate the polymerization process of thethermoplastic synthetic polymer in the second blend. Preferably, theinitiator is selected from any one or combination of Sodium peroxide,Tert-butyl hydroperoxide, Di-tert-butyl peroxide, and Dicumyl peroxide.

The disclosed invention also includes plasticizer in order to have thestarch-containing agricultural waste attached the desired plasticity tobe workable in further process. Owing to the fact that starch hasmelting temperature approaches the decomposition temperature, mereheating the starch-containing agricultural waste fail to completelytransform the starch in the waste into its molten state while the moltenstate of the starch can only be attained in the addition of plasticizerin the TPS forming process. The plasticizer described herein shall referto any suitable plasticizer capable of producing TPS composition. Theplasticizer is any one or combination of sugar alcohol, polyols,sorbitol ethoxylate, glycerol ethoxylate, pentaerythritol ethoxylate,sorbitol acetate, pentaerythritol acetate, water, urea or ureaderivatives, anhydrides of sugar alcohols, phthalate esters, dimethyland diethylsuccinate and related esters, glycerol monoacetate, glyceroldiacetate, glycerol triacetate, glycerol mono acid esters, citric acidesters, adipic acid esters, stearic acid esters, oleic acid esters,copolymers of ethylene and acrylic acid, polyethylene grafted maleicacid, polybutadiene-co-acrylic acid, polybutadiene-co-maleic acid,propylene-co-acrylic acid, polypropylene-co-maleic acid and otherhydrocarbon based acid, adipic acid derivatives, benzoic acidderivatives, citric acid derivatives, phosphoric acid derivatives,sebacic acid derivatives, onoglyceride, diglycerides, acetylatedmonoglyceride, acetylated glycerol monostearate, acetylated glycerolmonoester-12-hydroxystearic acid, acesters of glycerin, glycerolmonopropionate, glycerol dipropionates and tripropionates, butanoates,stearates, alkylamides, trimethylolpropane, dimethyl sulfoxide, mannitolmonoacetate, and mannitol monoethyoxylate.

To gain better compatibility and dispersion characteristics of thestarch and the thermoplastic synthetic polymer in the produced TPScomposition, coupling agent, also known as compatibilizer, is used. Thecoupling agent can be placed in the mixture for compounding with thefunctionalised agricultural waste. As described above, the couplingagent is added into the second blend in the embodiment having separatedblends for the compounding. Under heated and pressurized environment,presence of the coupling agent promotes covalent linkage formation inbetween the starch and the thermoplastic synthetic polymer. Morespecifically, the coupling agents are generally hydrophobic polymerswhich carries a functional group particularly to react and bind withhydroxyl group in the starch while the rest of the hydrophobic portioninteracts with the thermoplastic synthetic polymer. The additioncoupling agent allows the starch to indirectly bind with thethermoplastic synthetic polymer therefore forming a physically strongcomposition collectively. Relying on the types of thermoplasticsynthetic polymer used and the derived TPS composition, the couplingagent can be any one or combination of ethylene vinyl acetate, ethylenevinyl alcohol, polyethylene-co-acrylic acid, polyethylene grafted maleicanhydride, maleic anhydride modified polyolefin, maleic anhydride,acrylic acid, vinyl acetate, vinyl alcohol, amino, amide or acrylate,polyvinyl-alcohol-co-vinyl acetate copolymer, ethylene/vinylalcohol/vinyl acetate copolymers, ethylene/vinyl chloride/vinylalcohol/vinyl acetate graft copolymers, vinyl alcohol/vinylacetate/vinyl chloride/diacryl amide copolymers, vinyl alcohol/vinylbutyral copolymers, vinyl alcohol/styrene copolymers, poly acrylicacid-co-vinyl acetate copolymer, ethylene/acrylic acid/vinyl acetatecopolymers, ethylene/vinyl chloride/acrylic acid/vinyl acetate graftcopolymers, acrylic acid/acrylonitrile copolymer,ethylene/propylene/acrylic acid copolymer, styrene/acrylic acidcopolymers, vinyl benzyl amino ethyl amino propyl trimethoxy silane,glycidyl methacrylate modified polymers, graft copolymers of methylmethacrylate

One of the embodiments of the produced TPS composition includes as wellfiller. Preferably, the filler is mixed with the first blend or themixture directly according to the mode of operation in producing the TPScomposition. It is in an amount of 25 to 35% by weight of totalcomposition. The resulting TPS composition can greatly affected by thechemical and physical properties of the filler especially the rheologyof the formed TPS. Depending on its melting point, the filler maypresent as discrete particles separated from the bound matrix of thestarch and the thermoplastic synthetic polymer or being melted topartially or completely integrated into the bound matrix of the starchand the thermoplastic synthetic polymer. With melting temperature higherthan the processing temperature, presence of the solid fillerparticulate, in the molten starch and thermoplastic synthetic polymerincrease the viscosity of the total mixture thus affecting themorphology of the derived TPS composition. More preferably, the fillerin the present invention is made of organic material or being naturalorigin which is any one or combination of wood, kenaf, coconut husk,rice husk, seagel, cork, seeds. The natural filler is preferablyprepared into the form of pulverized powder with a particle size notmore than 170 micron. Nonetheless, other inorganic or metal filler likemetallic flakes may be incorporated in the disclosed TPS composition inother embodiments relying upon the TPS composition resulted.

To further improve workability and flexibility of the disclosed TPScomposition, the disclosed invention, in one embodiment, includeslubricating agent in 0.2 to 2% by weight of total composition.Preferably, the lubricating agent is inert in relative to theplasticizer and prepared in the first blend. The lubricating agent canbe selected from any one or combination of non-metallic stearates,paraffin wax, polyester wax, stearyl stearate, distearyl phthalate,pentaerythritol adipate stearate, ethylene glycol distearate,pentaerythritol tetrastearate, glycerol tristearate, polyethylene glycolmonostearate, glycerol monooleate, glycerol distearate, N,N-ethylenebis-stearamide, fatty acids derivatives and the like.

Still, the TPS composition, particularly in the first blend, may furthercomprise antioxidant or ant-oxidative agent in an amount of 0.2 to 1% byweight of total composition to prevent polymer degradation in the TPSforming process caused by the applied heat.

To improve aesthetic effect of the products derived from the TPScomposition, the second blend forming the disclosed TPS composition maybe further furnished with coloring agent in an amount of 3 to 10% byweight of total composition in one of the embodiments. The coloringagent can be of organic or inorganic origin or azo dyes. Still, colormasterbatch of 3 to 10% by weight of total composition is added into thesecond blend to impart the desired color to the produced TPScomposition. Another embodiment of the disclosed composition may haveadditive masterbatch in the amount of 0.1 to 10% by weight of totalcomposition processed together with the first and second blends toproduce TPS composition with improved physiochemical propertiesparticularly in antistatic, anti-microbial, anti-oxidative, corrosionresistance, UV resistance and so on.

Pursuant to another preferred embodiment, the present invention alsodisclosed a method of producing thermoplastic starch compositioncomprising the steps of compounding starch-containing agricultural wastetogether with a mixture of a thermoplastic synthetic polymer in 25 to50% by weight of total composition, a plasticizer in 1 to 10% by weightof total composition, and a coupling agent in 1 to 5% by weight of totalcomposition at a first temperature higher than room temperature, whereinthe starch-containing agricultural waste is 45 to 70% by weight of totalcomposition and the agricultural waste contains starch content less than50% in dry weight. Preferably, the disclosed method further comprisesthe step of reacting the starch-containing agricultural waste with areactant having functional group selected from the group consisting ofprimary alkylamine, secondary alkylamine, tertiary alkylamine, stearateester, oleate ester, ecucate ester, ethoxy, methoxy, silane, vinyl,hydroxyl or any combination thereof at a second temperature, which ishigher than room temperature but lower than the first temperature, priorto the compounding step. Accordingly, the first temperature is 140° C.to 170° C. while the second temperature is around 65° C. to 105° C.

Like in the foregoing description, the agricultural waste used in thedisclosed method is relatively lower in starch content compared tocommercially available product. Particularly, the agricultural waste ofthe present invention contains starch content less than 50%, morepreferably 15% to 50%, in dry weight and amylose content lower than 20%.Food crops used in conventional TPS production contains more than 70% indry weight of starch content and amylose content not lower than 25% byweight. Presence of large amount of non-starch material, such as fibrecontent not lower than 10% by weight, requires the agricultural waste tobe pre-treated or functionalised first before proceeding to compounding.Preferably, the agricultural waste is pulverized powder of, but notlimited to, tamarind kernel, ratanjot, castor seed, Jatropha seeds,moringa seed, neem seed, cocoa bean skin, coffee bean skin, rice husk,sugar cane bagasse, coconut fiber, palm oil fruit bunch, wood chips, andsaw dust. Apart from that, the disclosed method can utilize as wellsolid waste produced in starch processing activities from food cropslike tapioca, yam, taro, konjac, potato or burdock.

In one embodiment, the mixture further comprising an initiator in 0.01to 5% by weight of total composition that the initiator is selected fromany one or combination of Sodium peroxide, Tert-butyl hydroperoxide,Di-tert-butyl peroxide, and Dicumyl peroxide. Similarly, the mixture mayfurther comprise as well a filler in 25 to 35% by weight of totalcomposition, an antioxidant in 0.2 to 1% by weight of total composition,coloring agent in 3 to 10% by weight of total composition or anycombination derived thereof.

In order to obtain the TPS composition of desired physiochemicalproperties, the plasticizer used in the disclosed method can be any oneor combination of sugar alcohol, polyols, sorbitl ethoxylate, glycerolethoxylate, pentaerythritol ethoxylate, sorbitol acetate,pentaerythritol acetate, water, urea or urea derivatives, anhydrides ofsugar alcohols, phthalate esters, dimethyl and diethylsuccinate andrelated esters, glycerol monoacetate, glycerol diacetate, glyceroltriacetate, glycerol mono acid esters, citric acid esters, adipic acidesters, stearic acid esters, oleic acid esters, copolymers of ethyleneand acrylic acid, polyethylene grafted maleic acid,polybutadiene-co-acrylic acid, polybutadiene-co-maleic acid,propylene-co-acrylic acid, polypropylene-co-maleic acid and otherhydrocarbon based acid, adipic acid derivatives, benzoic acidderivatives, citric acid derivatives, phosphoric acid derivatives,sebacic acid derivatives, onoglyceride, diglycerides, acetylatedmonoglyceride, acetylated glycerol monostearate, acetylated glycerolmonoester-12-hydroxystearic acid, esters of glycerin, glycerolmonopropionate, glycerol dipropionates and tripropionates, butanoates,stearates, alkylamides, trimethylolpropane, dimethyl sulfoxide, mannitolmonoacetate, and mannitol monoethyoxylate.

In another embodiment of the disclosed method, the mixture furthercomprises a processing aid in 0.2 to 2% by weight of total compositionselected from any one or combination of non-metallic stearates, paraffinwax, polyester wax, stearyl stearate, distearyl phthalate,pentaerythritol adipate stearate, ethylene glycol distearate,pentaerythritol tetrastearate, glycerol tristearate, polyethylene glycolmonostearate, glycerol monooleate, glycerol distearate, N,N-ethylenebis-stearamide, and fatty acids derivatives.

Example 1

In order to prepare sample 1, the starch residue (waste) is pre-treatedor functionalized with alkyl amine and esters blends in the presence ofdicumyl peroxide in a high speed mixer that are able to be heated up to120° C. for a period of 10 min. After this pre-treatment process,Di-substituted glycerol will be added into the starch residue and mixedfor 5 min prior to the addition of other components like calciumstearate, butylated hydroxytoluene, acetate copolymers and PP to bemixed for a further 5 min before discharging the mixed composition intoa gravimetric feeder of a twin screw extruder for reactiveextrusion/compounding process to take place. The setting of thetemperature for reactive extrusion and compounding process is 140-170°C. for the barrels and the screw speed is 200 rpm. Resins obtained fromthe twin screw extruder is then dried at 80° C. for a minimum of 2 hrsbefore sheet extrusion using a single screw extruder with an L/D of 25to produce extruded sheet having a thickness of 0.5 mm and width of 370mm for mechanical tests using a Universal Tensile Testing machine. Thedumbbell test pieces are conditioned for a period of 48 hrs at 20°C./55% RH before tests.

For acquiring sample 2, the kernel powder (waste) is pre-treated orfunctionalized with silanol in the presence of dicumyl peroxide in ahigh speed mixer that are able to be heated up to 120° C. for a periodof 10 min. After this pre-treatment process, amides and fatty acidsderivatives will be added into the kernel powder and mixed for 5 minprior to the addition of other components like oxidized PE wax,butylated hydroxytoluene, maleic anhydride grafted polystyrene andpolystyrene (PS) to be mixed for a further 5 min before discharging themixed composition into a gravimetric feeder of a twin screw extruder forreactive extrusion/compounding process to take place. The setting of thetemperature for reactive extrusion and compounding process is 140-160°C. for the barrels and the screw speed is 200 rpm. Resins obtained fromthe twin screw extruder is then dried at 80° C. for a minimum of 2 hrsbefore sheet extrusion using a single screw extruder with an L/D of 25to produce extruded sheet having a thickness of 0.5 mm and width of 370mm for mechanical tests using a Universal Tensile Testing Machine. Thedumbbell test pieces are conditioned for a period of 48 hrs at 20°C./55% RH before tests.

Mechanical properties of the sample 1 and 2 are presented in table 1below.

TABLE 1 Formulations Sample 1 Sample 2 Agricultural waste (wt %)60^(a )   60^(I) Fossil based plastics (wt %) 30.3^(b)    30.3^(II)Compatibilizers (wt %) 2^(c  )   2^(III) Plasticizer (wt %) 5^(d)    5^(IV) Surface Modifier (wt %) 0.5^(e)    0.5^(V) Catalyst (wt %)0.2^(f )   0.2^(VI) Processing aid (wt %) 1.5^(g)    1.5^(VII)Antioxidant (wt %) 0.5^(h)    0.5^(VIII) Mechanical Properties MaximumStress (MPa) 12    18 Elongation at break (%) 130    15 Young Modulus(MPa) 1170     1930  Notes: ^(a)Starch residue ^(b)PP ^(c)acetatecopolymers ^(d)Di-substituted glycerol ^(e)alkyl amine and esters blends^(f)Dicumyl peroxide ^(g)calcium stearate ^(h)butylated hydroxytoluene^(I)Kernel powder ^(II)PS ^(III)maleic anhydride grafted PS ^(IV)amidesand fatty acids derivatives ^(V)Silanol ^(VI)Dicumyl peroxide^(VII)Oxidized PE wax ^(VIII)butylated hydroxytoluene

Example 2

Carbon footprint of sample 1 in example 1 (from cradle to polymerfactory gate) was calculated according PAS 2050 [1]. The PAS 2050 allowsimmaterial emissions to be excluded i.e. any single source resulting inless than 1% of total emissions. However, the total proportion ofimmaterial emission sources cannot exceed 5% of the full product carbonfootprint. Hence the carbon footprint for surface modifier, catalyst,compatibilizers and other additives have been excluded.

For the starch residue, calculation include diesel used for thetransportation from supplier (i.e. 13 kg of diesel for a 26 km distance)as well as electricity used for the processing e.g., drying andpulverization of starch residue (i.e., 0.26 kWh/kg of starch residues).The energy use for the cultivation of the plant where the starch comefrom is excluded as the present invention is using only the waste orstarch residue from the starch production.

For the recycle PP, calculation include diesel used for thetransportation from supplier (i.e. 5 kg of diesel for a 10 km distance)as well as energy used for the pelletizing of recycle PP (0.06 kWh/kg ofrecycle PP). And the embodied energy for recycle PP is 36-44 MJ/kg andcarbon footprint is 1.1-1.2 kg, CO₂e/kg recycle PP as reported by M. F.Ashby [2].

For the Di-substituted glycerol, calculation include diesel used for thetransportation from supplier (i.e. 4 kg of diesel for a 8 km distance)as well as energy used for the production of Di-substituted glycerolwhich is obtained from the supplier (i.e. 52.33 MJ/kg of product and itsCO₂ emission is 1.96 kgCO₂e/kg of product).

Production energy for the TPS composition in Example 1 includeelectricity used for pre-mixing (i.e. 0.06 kwh/kg) as well aselectricity used for reactive extrusion (i.e. 0.94 kwh/kg) to produceExample 1 in resins form.

Fossil energy used for the transportation of the starch residues fromsupplier followed by the processing of starch residues=1.00 MJ/kg

Fossil energy used for the transportation of the recycle PP fromsupplier followed by the processing of the recycle plastics=36.20 MJ/kg

Fossil energy used for the production and transportation of theDi-substituted glycerol from supplier=52.35 MJ/kg

Fossil energy used for pre-mixing=0.22 MJ/kg

Fossil energy used for reactive extrusion=3.38 MJ/kg

Fossil energy for the manufacturing of Example 1=0.60 (1.00)+0.30(36.2)+0.05 (52.35)+0.22+3.38=17.7 MJ/kg

Carbon footprint used for the transportation of the starch residues fromsupplier followed by the processing of starch residues=0.16 kg CO₂e/kg

Carbon footprint used for the transportation of the recycle PP fromsupplier followed by the processing of the recycle PP=1.14 kg CO₂e/kg

Carbon footprint used for the production and transportation of theDi-substituted glycerol from supplier=1.96 kg CO₂e/kg

Carbon foot print used for pre-mixing=0.04 kg CO₂e/kg

Carbon foot print used for reactive extrusion=0.59 kg CO₂e/kg

Carbon footprint for the manufacturing of Sample 1=0.6 (0.16)+0.30(1.14)+0.05 (1.96)+0.04+0.59=1.17 kg CO₂e/kg

The calculated fossil energy consumption and carbon footprint of sample1 were used to compare with other materials. The comparison shows thatthe sample 1 of the disclosed composition is far more energy efficiencyand significantly lower in carbon footprint. The details of thecomparison are shown in FIGS. 2 and 3.

Changes therein and other uses will occur to those skilled in the artwhich are encompassed within the scope of the invention as defined bythe scope of the claims.

REFERENCE

-   [1] Specification for the assessment of the life cycle greenhouse    gas emissions of goods and services. PAS 2050:2011, [Online:    www.bsigroup.com/upload/Standards%20 . . . /Energy/PAS2050.pdf],    Publicly available references.-   [2] M. F. Ashby, Material Profiles, Materials and the environment:    eco-informed material choice, 2009, p 297-299.-   [3] E. T. H, Vink, S. Davies and J. J. Kolstad, The eco-profile for    current Ingeo® polylactide production. Industrial Biotechnology,    2010 (6), p 213-225 [Online]. Available from NatureWorks website    www.naturewoksllc.com.-   [4] J. Laurijssen, M. Marsidi, A. Westenbrook, E. Worrell, A. Faaji,    Paper and biomass for energy? The impact of paper recycling on    energy and CO ₂ emissions, Resources, Conservation and Recycling,    2010 (54), p 1208-1218,

The invention claimed is:
 1. A bio-resin, comprising: a heat-compoundedmixture of: 45% to 70% by weight of a starch-containing agriculturalbyproduct, the starch-containing agricultural byproduct having a starchcontent of less than 50% by dry weight; 25% to 50% by weight of athermoplastic synthetic polymer; 0.01% to 5% by weight of an initiator;and at least 1% by weight of a coupling agent.
 2. The bio-resin of claim1, wherein the mixture further includes at least one of: 0.2% to 1% byweight of an antioxidant, and 3% to 10% by weight of a coloring agent.3. The bio-resin of claim 1, wherein the mixture further includes atleast 25% by weight of a filler material.
 4. The bio-resin of claim 1,wherein the mixture further includes a fibrous natural filler material.5. The bio-resin of claim 1, wherein the mixture further includes anatural filler material including one or more of wood, palm oil waste,kenaf, coconut husk, and/or rice husk.
 6. The bio-resin of claim 1,wherein the mixture further includes a pulverized powder natural fillermaterial.
 7. The bio-resin of claim 1, wherein the mixture furtherincludes a natural filler material with an average particle size of 170microns or less.
 8. The bio-resin of claim 1, wherein thestarch-containing agricultural byproduct has an amylose content lessthan 20% dry weight.
 9. The bio-resin of claim 1, further comprising0.01% to 10% by weight of a plasticizer.
 10. The bio-resin of claim 9,wherein the plasticizer is one or more of the following: sugar alcohol,polyols, sorbitol ethoxylate, glycerol ethoxylate, pentaerythritolethoxylate, sorbitol acetate, pentaerythritol acetate, water, urea, ureaderivatives, sugar alcohol anhydrides, phthalate esters,dimethylsuccinate, diethylsuccinate, esters of dimethylsuccinate, estersof diethylsuccinate, glycerol monoacetate, glycerol diacetate, glyceroltriacetate, glycerol mono acid esters, citric acid esters, adipic acidesters, stearic acid esters, oleic acid esters, copolymers of ethyleneand acrylic acid, polyethylene grafted maleic acid,polybutadiene-coacrylic acid, polybutadiene-co-maleic acid,propylene-coacrylic acid, polypropylene-co-maleic acid, adipic acidderivatives, benzoic acid derivatives, citric acid derivatives,phosphoric acid derivatives, sebacic acid derivatives, monoglyceride,diglycerides, acetylated monoglyceride, acetylated glycerol monostearate, acetylated glycerol monoester-12-hydroxystearic acid, aceticacids esters of glycerol, glycerol monopropionate, glyceroldipropionates and tripropionates, butanoates, stearates, alkylamides,trimethylolpropane, dimethyl sulfoxide, mannitol monoacetate, and/ormannitol monoethyoxylate.
 11. The bio-resin of claim 1, wherein thethermoplastic synthetic polymer is one or more of the following: avinylpolymer; a polyvinyl carbazol; a polystyrene; a polylactide; apolyester; a poly(alkylene terephthalate); a polyacrylonitrile; apoly(alkylene oxide); a polyimide; a polyarylether; a polycarbonate; apolyolefin; a styrenic copolymer; an ethylene vinyl acetate copolymer;an ethylene vinyl alcohol copolymer; an ethylene acrylic acid copolymer;an ethylene ethyl acrylate copolymer; an ethylene methyl acrylatecopolymer; a acrylonitrile butadiene styrene copolymer; and/or a styreneacrylonitrile copolymer.
 12. The bio-resin of claim 11, wherein one ormore of: the vinylpolymer includes a polyvinyl alcohol and/or apolyvinyl acetate; the polyester includes a poly(hydroxybutyrate) and/ora polyhydroxyl adipate; the polyolefin includes a polypropylene, apolyethylene, and/or a polyisobutylene; and/or the styrenic copolymerincludes an acrylonitrile butadiene styrene copolymer, a styreneacrylonitrile copolymer, a styrene ethylene butadiene copolymer, and/ora styrene ethylene butylene styrene copolymer.